1. Field of the Invention
The present invention relates to a controller designed to perform simultaneous fuel injection to all cylinders and simultaneous ignition control for each group of cylinders, which is to be ignited, of a four-stroke cycle internal-combustion engine (hereinafter referred to simply as "engine") and, more particularly, to a controller for the four-stroke cycle internal-combustion engine, which controller realizes better engine controllability by preventing a problem at the time of controlling the simultaneous ignition especially at start-up or the like.
2. Description of the Related Art
A conventional four-stroke cycle internal-combustion engine electronically controls the fuel injection timing, the ignition control timing, and the like of the engine by generating a positional signal for each cylinder which synchronizes with the revolution of the engine and by controlling the fuel injection timing and the ignition timing in accordance with the positional signal. Normally, a well-known rotation signal generator designed for detecting the rotation of a camshaft or a crankshaft of an engine is used as the means for generating a positional signal which corresponds to the reference position of each cylinder.
FIG. 6 is a block diagram showing a typical controller for a four-stroke cycle internal-combustion engine. In the drawing, a rotation signal generator 9 functioning as an angle detector issues an angle signal POS of the engine and a reference position signal REF which corresponds to each cylinder. Various sensors 10 other than the rotation signal generator 9 detect the operating state of the engine and output operating state information D.
The angle signal POS, the reference position signal REF, and the operating state information D (sensor signals) are supplied to a microprocessor 12, which carries out fuel injection control and ignition control, via an input interface circuit 11. The microprocessor 12 drives an injector 14 for injecting fuel and also alternately drives ignition coils 15 and 16 for generating high voltage for ignition via an output interface circuit 13.
The injector 14 injects fuel to all cylinders at each control timing and the ignition coils 15 and 16 are driven for each group of cylinders to be ignited, which has a different control timing and which will be discussed later, thereby performing the simultaneous ignition control for each group of cylinders.
The input interface circuit 11, the microprocessor 12, and the output interface circuit 13 constitute an electronic control unit (ECU) 100 for controlling the engine. The microprocessor 12 includes a fuel injection control unit for injecting fuel to each cylinder at the same time and an ignition control unit for performing control so as to cause a spark plug (not shown) to be simultaneously discharged for a cylinder group to be ignited.
FIG. 7 is a perspective view showing a specific example of the configuration of the rotation signal generator 9 shown in FIG. 6. FIG. 8 is a circuit diagram with a partial block diagram showing the position signal generator in the rotation signal generator 9. In FIG. 7, a rotary shaft 1 which rotates in synchronization with an engine is integrally connected to a camshaft which, for example, rotates once in synchronization with one cycle of the operation of each cylinder of the engine. The camshaft reduces the number of revolutions of a crankshaft (not shown), which is directly connected to the engine, to a half.
A rotary disc 2 attached to the rotary shaft 1 has a plurality of slit windows 3 and 4 which are provided equidistantly in the direction of rotation (indicated by the arrow).
The positions of the windows 3 are keyed to the angle signal POS which is issued repeatedly for every predetermined angle of the engine; the positions of the windows 4 are keyed to the reference position (predetermined angle of rotation) signal REF for each cylinder.
This example shows a case where the four-stroke cycle internal-combustion engine has four cylinders (#1 to #4); the outer periphery of the rotary disc 2 has the slit windows 3 for generating the angle signal POS which reverses at every predetermined angle of the engine; and four windows 4 for generating the reference position signal REF for each cylinder are provided in the middle of the rotary disc 2.
The end of each window 4 which is located at the front with respect to the direction of rotation is keyed to the reference position of each cylinder. The width of each window 4 differs in the respective cylinders (#1 to #4), so that a particular cylinder and each cylinder can be identified by measuring the width of the window 4.
A pair of light emitting diodes 5 are arranged to face the windows 3 and 4, respectively; a pair of photodiodes 6 are arranged to receive light emitted from the light emitting diodes 5 through the windows 3 and 4. These light emitting diodes 5 and the photodiodes 6 constitute two pairs of photo couplers.
In FIG. 8, an amplifier 7 amplifies the output signals issued by the photo diodes 6. An output transistor 8 with open collector (with common emitter) has its base connected to the output terminal of the amplifier 7. The collector terminal of the output transistor 8 is connected to the input interface circuit 11 (see FIG. 6).
It should be noted that a plurality of circuits having the same configuration as that shown in FIG. 8 are provided for the respective windows 3 and 4 although the example shows only one train for the purpose of convenience.
FIG. 9 shows the waveforms indicative of the timings for generating the angle signal POS and the reference position signal REF.
In FIG. 9, the positional signal obtained based on the windows 3 is the angle signal POS; the positional signal obtained based on the windows 4 is the reference position signal REF which provides the crank angle reference signal and it reverses at a predetermined crank angle for each of the cylinders #1 to #4.
The reference position signal REF used to control the timings for the fuel injection and ignition of the engine indicates that each rise coincides with a crank angle reference position B110 degrees (110 degrees before reaching a top dead center TDC) for each cylinder; the signal width thereof differs to enable the respective cylinders to be identified. The pulse width of each reference position signal REF is set to about 8, 12, 16, and 20 degrees in terms of the crank angle, for example.
FIG. 10 is an illustrative diagram showing the fuel injection controlling procedure (the hatched portions) of the injector 14 at the start-up and the ignition controlling procedure (indicated by the arrows) of the ignition coils 15 and 16. The fuel injection timing and the ignition control timing are keyed to the respective cylinders (#1 to #4) to provide a timing chart shown in time series.
In FIG. 10, the cycle related to the cylinders (#1 to #4) consists of four strokes, namely, the induction stroke, the compression stroke, the power stroke, and the exhaust stroke. In the order of #1, #3, #4, and #2, the cycles are shifted by one stroke.
The fuel injection timing (hatched) for each cylinder corresponds to the crank angle reference position (B110 degrees). The ignition control timing (arrow) for the spark plug of each cylinder corresponds to the moment immediately following the compression.
In this case, the fuel injection is performed for a single cylinder by a bisectional control method. For cylinder #1, for example, the first fuel injection (hatched) is carried out during the power stroke immediately after the ignition control (arrow), then the second fuel injection (hatched) is implemented during the induction stroke following the exhaust stroke. Thus, the required amount of fuel is supplied in two steps.
In the cycle immediately after the startup (leftmost cycle in FIG. 10), only fuel injection is performed and no ignition control is performed (no stroke indicated by the arrow is given).
The operation of the controller for the conventional four-stroke cycle internal-combustion engine shown in FIG. 6 through FIG. 8 will now be described with reference to FIG. 9 and FIG. 10.
When the rotary shaft 1 and the rotary disc 2 rotate as the engine starts, the rotation signal generator 9 generates the two types of positional signals, namely, the angle signal POS and the reference position signal REF (see FIG. 9).
More specifically, the photodiodes 5 of the two pairs of photo couplers, which are arranged so that they face against each other with the windows 3 and 4 of the rotary disc 2 located between them, generate pulse signals which rise at the front ends of the respective slits constituting the windows 3 and 4 and fall at the rear ends thereof. The amplifier 7 and the output transistor 8 shape the waveform of the pulse signals to issue the angle signal POS and the reference position signal REF.
The angle signal POS and the reference position signal REF are supplied to the microprocessor 12 via the input interface circuit 11; the microprocessor 12 issues a control signal via the output interface circuit 13 and drives the injector 14 in synchronization with the rise of the reference position signal REF so as to supply fuel to the respective cylinders. The microprocessor 12 also measures the signal width of the reference position signal REF in accordance with the count value of the angle signals POS and as soon as it identifies the reference position signal REF of a particular cylinder, it drives the ignition coil 15 or 16 of the cylinder group.
The operation stated above will now be described in detail in conjunction with FIG. 10.
First, when the microprocessor 12 detects the rise of the reference position signal REF (reference position B110 degrees of each cylinder), it simultaneously drives and controls the injectors 14 of all cylinders. Then, the microprocessor 12 detects the pulse signal width of the reference position signal REF by counting the angle signals POS so as to identify the cylinder which corresponds to the present crank angle reference position B110 degrees.
Upon completion of the detection of the cylinder, the microprocessor 12 replaces the crank angle reference position B110 degrees with the timing reference position for the ignition control and drives and controls the ignition coil 15 or 16 which corresponds to the cylinder group which is to be ignited and controlled simultaneously (#1 and #4 or #3 and #2) (see the arrows shown in FIG. 10).
After that, the drive and control of the injector 14 is performed once for each rotation of the crankshaft (half the rotation of the camshaft). The ignition control by driving the ignition coils 15 and 16 is carried out once for each half rotation of the crankshaft (a quarter rotation of the camshaft); it is repeated alternately on the groups of cylinders to be ignited.
The aforesaid conventional four-stroke cycle internal-combustion engine controller, however, presents the following problem especially at the time of starting the engine.
The ignition timing (timing point A shown in FIG. 10) in cylinder #3 coincides with the point immediately after the exhaust stroke of cylinder #2, i.e. immediately before the induction stroke, and it corresponds to the ignition control timing for the cylinder on the dead ignition side. Hence, at timing point A, the discharge timing of the spark plug for the cylinder on the dead ignition side (cylinder #2), which timing is controlled by the ignition control processing, in the group of cylinders (#3 and #2) corresponds to the point immediately before the induction stroke (latter half of the exhaust stroke), thus overlapping the timing at which the intake valve is opened.
At the upstream of the intake valve, the injector 14 is driven at two different timings (during the compression stroke and the exhaust stroke) before the present ignition control is performed, thus rendering a condition in which the injected fuel is charged and an air-fuel ratio enabling combustion is obtained. Therefore, when the intake valve is opened, the cylinder on the dead ignition side is fired, resulting in a problem of a backfire into an intake port.
The problem, as stated above, tends to take place when the engine is started up whereas it is unlikely to happen during the normal operation. This is because during the normal operation, once the combustion is accomplished in a cylinder by the ignition control, the required fuel will not be accumulated at the upstream of the intake valve unless two fuel injections follow.
Thus, the conventional controller for the four-stroke cycle internal-combustion engine is designed to perform the fuel injection control for all the cylinders in two steps and carry out the simultaneous ignition control of the cylinder group immediately after the second fuel injection, presenting a problem such as a backfire into the intake port due to a cylinder on the dead ignition side being ignited especially at the startup of the engine.